1. Field of the Invention
The present invention is directed to biopsy needle assemblies for use with biopsy gun devices known in the prior art and, more specifically, to an integrated biopsy needle assembly capable of being readily inserted within and removed from such devices.
2. Background Art
Various devices for obtaining tissue samples from a living being are previously known in the art. One such device is known as a “biopsy gun”, which typically includes an outer cannula and inner stylet that are “fired” in sequence in order to obtain and sever a sample of tissue. One such previously-known device is disclosed in Schramm et al., U.S. Pat. No. 5,476,101. The device disclosed by Schramm et al. utilizes a separate cannula and stylet, each having sharpened distal ends for penetrating tissue, as is well known in the art. The proximal ends of the cannula and the stylet are operably fixed to respective hubs, which are adapted to be retained in corresponding yokes contained within the biopsy gun. The stylet also includes a hollowed-out tissue sampling recess near the distal end thereof. The separate cannula and stylet are joined, prior to use, by inserting the stylet within the hollow cannula. Once so joined, the needle assembly can then be inserted into the biopsy gun, by inserting the cannula and stylet hubs within the corresponding yokes, which serve to maintain the position of the cannula and stylet relative to one another during use of the device.
In order to obtain a tissue sample, the biopsy gun must first be “cocked” to prepare it for use, as disclosed in Schramm et al. Once the gun has been cocked, the distal ends of the cannula and stylet are then inserted into the tissue region from which a sample is desired. After the distal ends of the cannula and stylet are placed at the desired location, the gun is then “fired”, causing the yoke associated with the stylet to be easily propelled forward, thereby exposing the tissue sampling recess associated with the stylet, and causing a tissue sample to prolapse into the recess. Next, the yoke associated with the cannula is propelled forward in rapid succession, so that the cannula once again covers the tissue sampling recess on the stylet, thereby causing the sharpened distal end of the cannula to sever the tissue sample contained within the tissue sampling recess. The tissue sample may then be retrieved by first removing the distal ends of the cannula and stylet from the tissue, then removing the cannula and stylet assembly from the biopsy gun, and finally retracting the cannula relative to the stylet in order to expose the tissue sampling recess.
Biopsy gun devices such as those disclosed by Schramm et al. require that separate cannula and stylet elements be joined prior to use, with the respective hub elements then being inserted into the corresponding yokes within the biopsy gun. This use of a separate cannula and stylet adds an additional assembly step to the biopsy process. Also, after the tissue sample is taken and the needle assembly has been removed from the biopsy gun, the user must take extra care to ensure that the stylet does not accidentally slide out of the cannula, thereby affecting the tissue sample.
These concerns were previously addressed by Terwilliger, U.S. Pat. No. 6,110,129, and Terwilliger, U.S. Pat. No. 6,328,701, which disclosed a biopsy needle for use in a biopsy gun, comprising a conventional cannula and stylet, and having a guiding needle holder including an integrated spacer, and first and second connecting elements. The first connecting element holds the proximal end of the cannula and is displaceably attached along the length of the integrated spacer. The second connecting element holds the proximal end of the stylet and is fixedly attached to the proximal end of the integrated spacer. The connecting elements each have an opening that facilitates insertion of the biopsy needle into a conventional biopsy gun. The integrated design ensures that the cannula and stylet are joined and properly oriented relative to each other prior to use, without the need for the user to manually insert the stylet into the cannula thereby facilitating the insertion of the needle assembly into the biopsy gun.
The needle assembly disclosed by the Terwilliger patents presents certain disadvantages of its own. Namely, the Terwilliger design, in which the stylet is operatively fixed to the integrated spacer, requires that the biopsy gun propel both the stylet and the integrated spacer when the stylet tip is first fired into the tissue to be sampled. As a result, a greater force may be required to be exerted on the stylet than would be required if the stylet were capable of moving relative to the integrated spacer. As a result, the biopsy gun must include a propelling means (typically, a spring) capable of providing sufficient force to accelerate both the stylet and the integrated spacer to the desired velocity. Additionally, the Terwilliger design can affect the retrieval of tissue samples from the stylet tissue sampling recess, due to the fact that the first connecting element is seated completely within the integrated spacer. As a result, it may be difficult for the user to manipulate the first connecting element, after the needle assembly has been removed from the biopsy gun, in order to retract the cannula from the stylet to expose the tissue sampling recess, and to remove the tissue sample therefrom.
It is therefore an object of the present invention to provide an integrated biopsy needle assembly for use with a conventional biopsy gun, in which the stylet is capable of movement relative to the spacer element, so as to minimize the amount of force needed to initially propel the stylet tip into the tissue to be sampled.
It is a further object of the present invention to provide a biopsy needle assembly in which retrieval of the tissue sample from the tissue sampling recess on the stylet is facilitated, by providing cannula and/or stylet hubs which are readily manipulable—so as to facilitate movement of the cannula and stylet relative to one another after the needle assembly has been removed from the biopsy gun.